In an image forming apparatus that forms a toner image, an electrostatic latent image is formed on a photoreceptor that is charged by a charger, based on image data. Then, the electrostatic latent image is developed with toner that is supplied from a developing unit. In such an image forming apparatus, the toner image on the photoreceptor may have uneven density in a width direction thereof for various reasons. For example, the uneven density of the toner image may be caused when a developing property of the developing unit is different in the width direction.